Labels... agreed that it would be on the tacky side... Your idea of using the "old" business cards for "personalization" is a good one! There are many times that a business card is given out to the same party or used as a "note card". Maybe could use them as appointment cards similar to those that physician offices and such use...? Where they write your appointment on the back of their card as a reminder...?
I love your idea of the personalization! What a way to recycle!